This grant proposal outlines a five-year training program required for the pursuit of an academic and research career in biomedical and dental sciences. The principal investigator is currently pursuing a PhD in Biomedical Sciences through the University of Florida College of Medicine and concomitantly will be beginning an orthodontic residency program through the College of Dentistry in the summer of 2003. This program will allow the principal investigator to gain competence in the areas of virology, genetics, molecular cell biology and biochemistry, by technical training in protein expression and purification, cell culture, mRNA inhibition, plasmid construction, viral vector use, and cell transduction. The immediate goals of this proposal are to 1) increase biological literacy, 2) gain skills in advanced techniques, and 3) stimulate critical thinking skills, with the ultimate goal being the preparation of Dr. Hurst for an independent career in academia and biomedical research. Dr. L. Shannon Holliday, PhD, an Assistant Professor in the Department of Orthodontics, will mentor the principal investigator in her research. Dr. Holliday studies the molecular and cellular biology of osteoclast activation, has expertise in the techniques involved in this study, and has numerous publications in the field of osteoclast biology. The extensive research community at the UF Health Science Center provides all of the necessary components, collaborative and physical, required to complete this proposal and allow the principal investigator to gain independence in research. Bone resorption by specialized cells called osteoclasts is required for normal physiology. However, enhanced bone resorption can cause severe disease, including osteoporosis and metastatic bone tumors. Although osteoclast-mediated diseases often do not share common etiologies, in each case, osteoclasts must form an acidic extracellular compartment to degrade bone. This project focuses on a region of tight contact between the osteoclast and bone, the sealing zone, which segregates this acidic compartment. Sealing zone formation is indispensable for bone resorption. As described in the research plan, a new hypothesis for how the Arp2/3 complex is involved in sealing zone formation has evolved from the principal investigator's studies. This project is designed to test this novel hypothesis and has three specific aims: first, to determine the requirement of Arp2/3 for the formation of the sealing zone in vivo; second, to characterize the Arp2/3 regulatory protein, cortactin; third, to characterize phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a regulatory protein of the Arp2/3 complex, in response to calcitonin and determine its effects on actin ring formation. By studying the structural, regulatory and functional roles of the Arp2/3 complex in the sealing zone, identification of new targets for gene therapy or conventional pharmaceuticals to inhibit resorptive bone diseases may be possible.